In the field of semiconductor device manufacturing, numerous efforts have been made to increase the density of semiconductor devices through their miniaturization. Recently, attention is being directed to a semiconductor device stacking technique called three-dimensional (3D) packaging as a means for increasing the density per unit area of semiconductor devices.
Semiconductor devices stacked in the vertical direction may include electrodes that are arranged to penetrate through a substrate including a silicon layer, for example. In this way, the semiconductor devices may be electrically connected via the electrodes. To create such an electrode that penetrates through a substrate, a resist is applied on the substrate using a coater, the resist is exposed using an exposure apparatus, and a resist pattern is developed using a developing apparatus. The resist is then used as a mask to etch the substrate using a plasma etching apparatus to create a hole such as a through hole or a via hole.
For example, when forming a hole such as a through hole in a substrate, plasma etching may have to be performed for a long period of time due to the substantial depth of the hole. On the other hand, as the semiconductor device is miniaturized, the resist film has to be made thinner in order to ensure shape accuracy. However, because the ratio of the silicon layer etching rate to the resist layer etching rate (i.e., selectivity) is not very high, when plasma etching is performed for a long period of time, the mask may be removed before etching is completed.
In this regard, a technique is known that involves using a silicon oxide film as a mask instead of a resist film in the case of forming a hole with a high aspect ratio (depth-to-inner diameter ratio) where the inner diameter is relatively small and the depth is substantially greater (see e.g., Patent Document 1). Because selectivity of the silicon layer to the silicon oxide film is higher than the selectivity of the silicon layer to the resist film, even when plasma etching is performed for a long period of time, the mask may be prevented from being removed before etching is completed.